1. Field of the Invention
This invention relates to an image compression processor for executing a compression processing for image information. More particularly, the invention relates to a real-time image compression processor for executing an image compression processing in real time in order to record the image information on a recording medium.
2. Description of the Related Background Art
As a system for compressing a video signal representing image information, there is known a real time image compression system which obtains a compressed video signal by executing, in real time, the compression processing of the video signal being reproduced from a VTR (video tape recorder) or the like.
As an example of such system, there is one wherein the compressed video signal is generated by compressively encoding the digital video signal which is reproduced from a VTR in accordance with the MPEG system, and then, the compressed video signal is transformed into the data format of a CD by a formatter thus obtained in order to record it on the CD consecutively. Since the recording rate of information data on a CD is constant, the parameters for the compression processing are set at a compression rate having a sufficient room so that the rate of generation of the recording signal will not exceed the recording rate even when the compressed video signal is produced in accordance with the video signal carrying complicated images.
Therefore, in the conventional real-time image compression processor, various parameters are determined for the encoder in anticipation of processing video signals which should carry a large amount of information. As a result, the compression processing is often carried out at a compression rate which is higher than the necessary rate in such a case where the objective video signal carries a comparatively small amount of information, thereby inviting a problem that the resultant image quality is degraded. Further, when the compressed video signal is obtained in accordance with the video signal whose amount of information is comparatively small, it is inevitable that the signal generation rate also becomes comparatively small against the recording rate. To counteract this, it is practiced that recording is made on a CD by adding null data subsequent to the video data. Here, a problem is again caused that the recording efficiency is lowered because such null data as irrelevant to image data must be recorded additionally.